/* 
* The contents of this file are subject to the Mozilla Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/MPL/
* 
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
* 
* The Original Code is the Netscape Portable Runtime library.
* 
* The Initial Developer of the Original Code is Netscape
* Communications Corporation.  Portions created by Netscape are 
* Copyright (C) 1994-2000 Netscape Communications Corporation.  All
* Rights Reserved.
* 
* Contributor(s):  Silicon Graphics, Inc.
* 
* Portions created by SGI are Copyright (C) 2000-2001 Silicon
* Graphics, Inc.  All Rights Reserved.
* 
* Alternatively, the contents of this file may be used under the
* terms of the GNU General Public License Version 2 or later (the
* "GPL"), in which case the provisions of the GPL are applicable 
* instead of those above.  If you wish to allow use of your 
* version of this file only under the terms of the GPL and not to
* allow others to use your version of this file under the MPL,
* indicate your decision by deleting the provisions above and
* replace them with the notice and other provisions required by
* the GPL.  If you do not delete the provisions above, a recipient
* may use your version of this file under either the MPL or the
* GPL.
*/

/*
* This file is derived directly from Netscape Communications Corporation,
* and consists of extensive modifications made during the year(s) 1999-2000.
*/

#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#ifndef WIN32
#include <sys/mman.h>
#endif
#include "common.h"


/* How much space to leave between the stacks, at each end */
#define REDZONE	_ST_PAGE_SIZE

_st_clist_t _st_free_stacks = ST_INIT_STATIC_CLIST(&_st_free_stacks);
int _st_num_free_stacks = 0;
int _st_randomize_stacks = 0;

static char *_st_new_stk_segment(int size);

_st_stack_t *_st_stack_new(int stack_size)
{
	_st_clist_t *qp;
	_st_stack_t *ts;
	int extra;

	for (qp = _st_free_stacks.next; qp != &_st_free_stacks; qp = qp->next) {
		ts = _ST_THREAD_STACK_PTR(qp);
		if (ts->stk_size >= stack_size) {
			/* Found a stack that is big enough */
			ST_REMOVE_LINK(&ts->links);
			_st_num_free_stacks--;
			ts->links.next = NULL;
			ts->links.prev = NULL;
			return ts;
		}
	}

	/* Make a new thread stack object. */
	if ((ts = (_st_stack_t *)calloc(1, sizeof(_st_stack_t))) == NULL)
		return NULL;
	extra = _st_randomize_stacks ? _ST_PAGE_SIZE : 0;
	ts->vaddr_size = stack_size + 2*REDZONE + extra;
	ts->vaddr = _st_new_stk_segment(ts->vaddr_size);
	if (!ts->vaddr) {
		free(ts);
		return NULL;
	}
	ts->stk_size = stack_size;
	ts->stk_bottom = ts->vaddr + REDZONE;
	ts->stk_top = ts->stk_bottom + stack_size;

#ifdef DEBUG
	mprotect(ts->vaddr, REDZONE, PROT_NONE);
	mprotect(ts->stk_top + extra, REDZONE, PROT_NONE);
#endif

	if (extra) {
		//long offset = (random() % extra) & ~0xf;
		long offset = (rand() % extra) & ~0xf;

		ts->stk_bottom += offset;
		ts->stk_top += offset;
	}

	return ts;
}


/*
* Free the stack for the current thread
*/
void _st_stack_free(_st_stack_t *ts)
{
	if (!ts)
		return;

	/* Put the stack on the free list */
	ST_APPEND_LINK(&ts->links, _st_free_stacks.prev);
	_st_num_free_stacks++;
}


static char *_st_new_stk_segment(int size)
{
#ifdef MALLOC_STACK
	void *vaddr = malloc(size);
#else
	static int zero_fd = -1;
	int mmap_flags = MAP_PRIVATE;
	void *vaddr;

#if defined (MD_USE_SYSV_ANON_MMAP)
	if (zero_fd < 0) {
		if ((zero_fd = open("/dev/zero", O_RDWR, 0)) < 0)
			return NULL;
		fcntl(zero_fd, F_SETFD, FD_CLOEXEC);
	}
#elif defined (MD_USE_BSD_ANON_MMAP)
	mmap_flags |= MAP_ANON;
#else
#error Unknown OS
#endif

	vaddr = mmap(NULL, size, PROT_READ | PROT_WRITE, mmap_flags, zero_fd, 0);
	if (vaddr == (void *)MAP_FAILED)
		return NULL;

#endif /* MALLOC_STACK */

	return (char *)vaddr;
}


/* Not used */
#if 0
void _st_delete_stk_segment(char *vaddr, int size)
{
#ifdef MALLOC_STACK
	free(vaddr);
#else
	(void) munmap(vaddr, size);
#endif
}
#endif

int st_randomize_stacks(int on)
{
	int wason = _st_randomize_stacks;

	_st_randomize_stacks = on;
	if (on)
		//srandom((unsigned int) st_utime());
		srand((unsigned int) st_utime());

	return wason;
}
